This application claims priority of pending German Patent Application 101 22 873.2 filed on May 11, 2001.
The invention relates to a flame atomization device, especially for an atom absorption spectrometer, with at least one mixer chamber and an atomizer leading into said mixer chamber, and with a burner head mounted on the mixer chamber""s burner connection piece.
Such a flame atomization device for an atom absorption spectrometer serves to bring a sample into a measurable atomic state. For this purpose, the sample is introduced by the atomizer, especially in the form of aerosol, into the mixer chamber. There, the sample is mixed with a fuel gas and conducted to the burner head via the burner connection piece. Then the fuel gas enriched with the sample combusts inside the burner head. The sample stimulated by the flame can be analyzed by the atom absorption spectrometer. In the course of regular operation, the speed with which the fuel gas enriched with the sample escapes exceeds the speed of combustion. Consequently, the corresponding flame is always found outside the mixer chamber or burner connection piece. Yet a certain kind of error, such as leaks or the use of laughing gas, may lead to flashbacks of the flame. Laughing gas for example, can lead to a very high combustion speed and is therefore difficult to handle.
During such a flashback of the flame, the flame burns inside the burner head, in the area of the burner connection piece, and possibly even in the remaining area of the mixer chamber. These areas possess comparatively large cross-sections in which the speed of the gas is low. This results in an explosion-like blow-up and a corresponding explosive excess pressure. Yet such an explosive excess pressure must not lead to the destruction of the components, and in addition, the flame atomization device should safely switch off in case such an excess pressure occurs.
With flame atomization devices currently in use, in cases of such explosive overpressure a corresponding pressure release was ensured, for instance by means of a burner head that flies off. The burner head was secured by a rope or other recovery devices. With other flame atomization devices, such a pressure relief occurred, for example, through a pretensioned pressure release valve.
Finally, there are known flame atomization devices, which use additional pressure relief devices such as removable plugs, a bursting disk, or something similar.
The flame atomization devices known from practice have the disadvantage of requiring additional parts, and of needing comparatively great cost when they have to be restored to working condition. Moreover, additional sealing areas are often required, which must be considered potential sources of errors.
The aim of the flame atomization device based on the invention is therefore to improve a device such as initially described, in such a manner as to provide a simple construction for pressure release, or respectively, pressure reduction, and at the same time, to restore the flame atomization device to working condition simply and quickly.
This aim is achieved by mounting a slip casing that can be adjusted between a closed position and an open position in relation to the burner connection piece. At the same time, in the open position, at least one pressure reduction outlet is opened in the burner connection piece.
Because of the sliding of the slip casing, it is unnecessary to include a component that flies off, or a component that is to be destroyed by the pressure. This also obviates the need to mount a comparatively complex pressure relief valve. When a correspondingly high degree of overpressure builds up, the slip casing automatically slides into its open position, and the pressure is reduced through the burner connection piece""s pressure reduction outlet. As a result, the pressure reduction outlet can be designed in such a way as to divert the escaping products without requiring additional, sensitive system parts. Likewise, such diversion may prevent injuries to personnel operating the device.
The slip casing may be located inside the burner connection piece in an adjustable manner. If the slip casing it is, for example, secured to the burner head in this position so that they move together, the slip casing may be slipped away together with the burner head when excess pressure occurs, and as a result, the pressure reduction outlet opens. Yet in order to configure the flame atomization device based on the invention in a simpler way and to avoid creating additional dead space inside the mixer chamber, which may lead to test delays between different samples, the slip casing can be mounted onto the burner connection piece from the outside. In this manner no modifications are required inside the burner connection piece.
The slip casing may also be configured as a partial covering; that is, the casing may only extend along a specific portion of the circumference around the burner connection piece. At the same time, the slip-casing may, as described above, be fixed to the burner head and, for example, be held in position by it, fitting tightly along one of the burner connection piece""s outer walls. If in such a case, the burner head moves because of excess pressure inside the mixer chamber, the slip casing or partial casing will move accordingly, as well, and the pressure reduction outlet is opened. Yet in order to enable the slip casing to be mounted independently from the burner head or from other parts of the flame atomization device, the slip casing may possess a slip mantle that encloses the burner connection piece. In this manner, the slip casing itself may be attached to the burner connection piece so that it is movable.
In order to fasten the slip casing to the burner head in a way that it can move only between the closed and open positions and cannot detach from the burner head by itself, the slip casing may be fastened to the burner connection piece by a clip.
In order to limit the slip casing""s freedom of movement between the closed and open positions, the slip casing may be mounted in a movable manner between the closed and open positions, yet at the same time be secured tightly onto the burning connection piece itself, in a way that prevents it from turning.
There are several ways to ensure such a type of mounting. A simple construction may include an essentially rib-like securing protrusion extending from the slip casing and/or the burner connection piece. This protrusion engages in a corresponding securing recess at the respective opposite part of the tightly secured, but axially movable bearing. In this manner, only one component is needed to ensure the mounting between the slip casing and the burner connection piece. At the same time, the closed and open positions may be determined by the sliding motion of the securing protrusion inside the securing recess. For example, the closed position may be determined by the securing protrusion""s contact with one end of the arresting recess, and the open position may be accordingly defined by the securing protrusion""s contact with the arresting depression""s other end.
In order to prevent the slip casing from getting wedged during its axial movement, it could be of advantage to arrange two securing protrusions, and their corresponding arresting depressions, diametrically opposite each other.
Within this context, it has to be noted that it is, of course, possible to design a securing protrusion on the slip casing as well as on the burner connection piece. In this case, accordingly, there is one securing recess each on the slip casing or the burner connection piece. The securing protrusions and recesses of the different components are arranged in such a way, in relation to each other, that they engage each other as soon as the slip casing is in position. In addition, it must be noted that the slip casing may also be clipped onto the burner connection piece by means of the securing protrusion and the arresting depression. For example, the slip casing is clipped onto the burner connection piece when the securing protrusion engages in the arresting depression.
In order to create, in a simple manner, a certain pressure on the slip casing in order to move it into the open position, the slip casing may be engaged in a detachable way with the burner connection piece. In order to release the engagement, a certain force is required, which corresponds in its strength to a corresponding excess pressure inside the mixer chamber.
A simple implementation of such an engagement may be achieved by arranging a pin element on the slip casing and/or burner connection piece and on the respective opposite part an opposing slot element. It may be of advantage, too, to arrange the pin element and opposing slot element in pairs, diametrically opposing each other.
A simple realization of such an opposing pin and slot element combination may be achieved by designing the pin element as a widening and the opposing slot element as an essentially complementary recess. The widening may, for example be created on an inner side of the slip casing, and correspondingly, the recess may be created on one of the burner connection piece""s outer sides. A reverse arrangement of pin and opposing slot element is possible, as well.
In order to allow a swift reduction of overpressure in the mixer chamber, even when the diameter of the pressure reduction outlet is small, a number (i.e. more than one) of pressure reduction outlets may be arranged in the burner connection piece, especially at an equal distance above the slip casing""s bottom edge in its closed position. The pressure reduction outlets may be distributed unevenly so that preferably the fuel gas, or alternatively the burned produce, escapes at a certain angle. Preferably, the pressure reduction outlets are arranged at the burner connection piece""s top end. Of course, it is equally possible to distribute the pressure reduction outlets unevenly, as far as their height is concerned, so that, for example, a pressure reduction occurs first from a smaller number of pressure reduction outlets, and in case of a higher excess pressure, finally, through all of the pressure reduction outlets. At the same time, corresponding pressure reduction outlets may be created, in addition, or even by themselves, in an area of the burner connection piece, an area which, when the slip casing is in open position, is open to the outside.
If, during a pressure build-up, there is no exertion of sensitive construction components in the mixer chamber""s area, the pressure reduction outlets may also be arranged in pairs, opposite each other, or at an equal distance from each other along the circumference of the burner connection piece. This causes a pressure reduction essentially in all radial directions in relation to the burner connection piece.
In order to allow a simple reaction to excess pressure within the mixer chamber, the burner head may be fastened to the slip casing in a detachable manner. If there is excess pressure in the mixer chamber, it will affect the burner head and move it in relation to the burner connection piece, together with the slip casing. Thus the slip casing is moved from its closed position into its open position.
A simple detachable fastening of the burner head and the slip casing may be achieved if the burner head can be clipped to the slip casing at the slip casing""s top end. This clipping connection must at least be sufficiently stable so that, when pressure is exerted on the burner head, the burner head does not detach from the slip casing and fly off uncontrollably, but instead moves the slip casing into its open position.
In order to be able to determine, preferably automatically, that there is overpressure inside the flame atomization device of this invention, which is reduced by moving the slip casing, the burner head""s and/or the slip casing""s movement may be recorded when the slip casing moves between its closed and open positions by means of a motion sensor device. If such a movement is registered, for example, a warning signal or something similar may be triggered.
A simple way to record such a position of the slip casing or the burner head is provided when the motion sensor device possesses at least one magnetic strip attached to the slip casing or the burner head, and a corresponding sensor. For example, the magnetic strip and the sensor may be arranged in relation to each other in such a way that the sensor reacts to the magnetic strip only when the slip casing is in its open position, thus triggering a warning signal.
In order to enable the burner head and slip casing to be fastened to each other in a simple way, a bayonet lock, especially one with two hooked noses shifted by 180xc2x0, may be arranged between the burner head and the slip casing.
In order to seal off the burner head and the slip casing from one other, and at the same time to ensure replacement of the burner head with little effort, a sealing element, especially an O-shaped ring, may be mounted between the burner head and the slip casing. If the pressure reduction outlets are located at the top end of the burner connection piece, the O-shaped ring seals the outlets against their surroundings when the slip casing is in closed position. At the same time, the O-shaped ring preferably is arranged below the pressure reduction outlets when in closed position. The pressure reduction outlets may be designed as slits or as fringe recesses opening toward the top edge of the burner connection piece.
In order to enable the burner head to be replaced or turned without problems, even when it is hot, the burner head may be equipped with a pivoted lever, which allows it to be fastened to and/or loosened from the slip casing. In such cases the pivoted lever is turned far enough to allow the bayonet lock between burner head and slip casing to be loosened, or alternatively to become engaged. Thereafter, the burner head may be removed or alternatively attached to the slip casing.
In order to mount the pivoted lever in a simple and swiveling manner, the pivoted lever may be equipped, at the end attached to the burner head, with a bearing section that is preferably circular in part. This section is fitted to the slip casing""s outside and may be swiveled in relation to the case.
In order to configure the pivoted lever as a component independent from the burner head, the bearing section may be located and held between one of the slip casing""s outer sides and one of the burner head""s inner sides. If the burner head is loosened from the slip casing, the pivoted lever with its bearing section may be removed, too, from the slip casing in a simple manner.
In order to simplify the bearing section""s arrangement between slip casing and burner head, the burner head""s inside may consist of a burner apron, which at least partially encases the slip casing. For example, the burner apron may extend partially around the slip casing, analogous to the bearing section.
When the burner head is attached to the slip casing by clipping, the pivoted lever may be attached to the burner head in a simple manner, when the bearing section and the burner apron are arranged with respect to one another in a way the prevents them from turning. This may be achieved, for example, by the engagement of corresponding protrusions and recesses in the area of the bearing section and burner apron.
In order to prevent, especially automatically, any additional damage to the flame atomization device from excess pressure, it may be possible to have the flame shut off at least when the motion sensor device registers the open position. This may be achieved, for example, by interrupting an electronically controlled fuel gas influx into the mixer chamber.
In order to be able to determine, in addition, whether the burner head is properly mounted onto the slip casing, the motion sensor device may be equipped with a detector, which registers either an angle position between burner head and slip casing and/or a type of burner head. This detector, too, may be composed of at least one magnetic strip and a matching sensor. It may be determined that the burner head is fastened properly to the slip casing, for example, by registering the magnetic strip on the slip casing only in such a pivoting range in which a proper fastening of the burner head on the burner connection piece is guaranteed. The bayonet lock is found between the burner head and the slip casing, when the slip casing is in closed position, only within this pivoting range.
Finally, the detector may also be used to register a type of burner head. In this case, for example, depending on the type of burner head, at least one corresponding magnetic strip changes its position at the burner head. At the same time, the magnetic strips may be designed separately in order to register the type of burner head and the angled position between the burner head and the slip casing.